Add or Remove Programs entry for Windows XP için Güvenlik Güncelleþtirmesi (KB899587). This security update for Windows XP addresses vulnerabilities in Kerberos that could allow denial of service, information disclosure and spoofing.

Kerberos Vulnerability: A denial of service vulnerability exists that could allow an attacker to send a specially crafted message to a Windows domain controller that could cause the service that is responsible for authenticating users in an Active Directory domain to stop responding.
PKINIT Vulnerability: This is an information disclosure and spoofing vulnerability. This vulnerability could allow an attacker to tamper with certain information that is sent from a domain controller and potentially access sensitive client network communication. Users could believe they are accessing a trusted server when in reality they are accessing a malicious server. However, an attacker would first have to inject themselves into the middle of an authentication session between a client and a domain controller.